Aircraft electrical systems usually include electrical components, devices, and equipment that require certain power quality characteristics. Thus, the aviation industry requires a programmable alternating current (AC) load that creates a variety of load profile functions. The programmable AC load may include combinations of passive components such as dissipative resistors, inductors, capacitors or motors. By changing or re-arranging the combination of these components, a limited number of load profiles may be generated. Some types of programmable AC loads also include semiconductors such as diodes and insulated-gate bipolar transistors (IGBTs).
Several drawbacks exist with the programmable AC loads currently available. For example, some programmable AC loads may only be capable of producing a limited number of load profiles. In particular, passive components and relatively slow power semiconductors may not be suitable for achieving some types of load profiles such as steady-state fundamental component profiles, harmonic load profiles, transient load profiles, modulation load profiles, and combinations thereof. In particular, diode bridge rectifiers may be used to generate harmonic load profiles. However, the harmonic patterns that are generated using the diode bridge rectifiers are very limited. Also, the passive components within the programmable AC load need to be adjusted in order to vary the magnitude and phase of the harmonic. Moreover, motor loads are typically used to achieve low frequency current modulation profiles. In this case, the modulation pattern is limited in terms of programmable current modulation magnitude and frequency as well as combining the modulation load profile with other types of load profiles, such as transient load profiles or harmonic load profiles.
In addition to the above-mentioned issues, many programmable AC loads currently available are purely dissipative. In other words, the energy processed by the programmable AC load to test a power source may be dissipated by heat, which is not cost-effective and unnecessarily wastes electrical energy. This issue may be further compounded if the programmable AC load is used in a test having a relatively long duration. Thus, there exists a need in the art for a more efficient, cost-effective programmable AC load that generates a wider variety of load profiles.